Low power rf tuning using optical and non-reflected power methods

ABSTRACT

Aspects of the present invention include methods and apparatuses that may be used for monitoring and adjusting plasma in a substrate processing system by using a plasma data monitoring assembly. In one embodiment, an apparatus for monitoring a plasma in a substrate processing system is provided. The apparatus includes a plasma chamber having a plurality of walls, at least one of the plurality of walls having a dielectric ceiling, at least one inner coil element and at least one outer coil element disposed outside the chamber, a current sensor coupled to one of the inner coil element or the outer coil element, the current sensor adapted to detect current from an inductively coupled plasma generated in the plasma chamber, an RF power source, and one or more adjustable capacitors coupled to each of the one or more coil elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/427,318 (Attorney Docket No. 010360USA), filed Jun. 28, 2006, whichis hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods and apparatuses foruse in substrate processing. More specifically, the present inventionrelates to plasma monitoring methods and apparatuses for use insubstrate processing using different processes, such as a PlasmaNitridation process and others.

2. Description of the Related Art

Integrated circuits have evolved into complex devices that can includemillions of components (e.g., transistors, capacitors, resistors, andthe like) on a single chip. The evolution of chip designs continuallyrequires faster circuitry and greater circuit density. The demands forgreater circuit density necessitate a reduction in the dimensions of theintegrated circuit components. The minimal dimensions of features ofsuch devices are commonly referred to in the art as critical dimensions.The critical dimensions generally include the minimal widths of thefeatures, such as lines, columns, openings, spaces between the lines,and device/film thickness and the like. As these critical dimensionsshrink, accurate measurement and process control becomes more difficult.

Importantly, in some cases, monitoring of implantation processes andcontrolling material thickness remain to be a challenge in substratedevice processing. For example, one problem associated with aconventional plasma process used in the manufacture of substrates is thelack of an ability to accurately monitor the formation of plasma andthereby accurately controlling the plasma state in a plasma chamberoperating with lower powers. One known method used to control a processattempts to achieve optimum power in a chamber by using a match circuitto transform the impedance of the plasma to a value that equals ormatches the characteristic impedance of the line through which RF poweris delivered to the chamber. At the match point, optimum power isdelivered into the plasma and little power is reflected back toward theRF supply. In this method, tuning the match circuit, which is controlledby a detector, is accomplished by varying the variable reactanceelements within the match circuit based on the power detected by adetector. Unfortunately, the impedance of plasma is a complex and highlyvariable function of many process parameters and thus requires constantmonitoring and adjustment by the detector. In addition, in some cases,the generator may not be capable of controlling lower powers and thusthe plasma may fluctuate during substrate processing.

Therefore, there is a need in the art for an improved method andapparatus for substrate monitoring and process control during themanufacture of integrated circuits.

SUMMARY OF THE INVENTION

One embodiment of the present invention provides a method for monitoringa plasma in a substrate processing system. The method includesmonitoring a first plasma condition generated by an inductively coupledplasma within a chamber, the chamber having one or more walls connectedby a dielectric ceiling, and one or more coil elements disposed outsidethe chamber, associating the first plasma condition to an RF powerwithin the processing system, adjusting a matching circuit to obtain arepeatable plasma condition, monitoring a second plasma conditiongenerated by the inductively coupled plasma within the chamber bymonitoring current to the one or more coil elements, and adjusting oneor more capacitors coupled to the one or more coil elements to maintainthe repeatable plasma condition.

Another embodiment of the present invention provides an apparatus formonitoring a plasma in a substrate processing system. The apparatusincludes a plasma chamber comprising a plurality of walls, at least onewall having a dielectric ceiling, one or more coil elements disposedoutside the chamber, a current sensor coupled to each of the one or morecoil elements, an RF power source, and one or more adjustable capacitorscoupled to each of the one or more coil elements.

Another embodiment of the present invention provides an apparatus formonitoring a plasma in a substrate processing system. The apparatusincludes a plasma chamber having a plurality of walls, at least one ofthe plurality of walls having a dielectric ceiling, at least one innercoil element and at least one outer coil element disposed outside thechamber, a current sensor coupled to one of the inner coil element orthe outer coil element, the current sensor adapted to detect currentfrom an inductively coupled plasma generated in the plasma chamber, anRF power source, and one or more adjustable capacitors coupled to eachof the one or more coil elements.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 illustrates an exemplary schematic diagram of a processing systemhaving one embodiment of the present invention;

FIG. 2 illustrates another exemplary schematic diagram of a processingsystem with an sensor for plasma monitoring;

FIG. 3 illustrates a cross section of the chamber wall of the system ofFIG. 2 having an optical sensor;

FIG. 4 illustrates a schematic of the tuning circuit in communicationwith a spectrometer according to an embodiment of the present invention;

FIG. 5 illustrates a diagram of a match peak find according to anembodiment of the present invention;

FIG. 6 illustrates a diagram of a match peak find according to anotherembodiment of the present invention; and

FIG. 7 illustrates a flow diagram of a processing method according to anembodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention provide methods and apparatusesthat may be utilized to monitor and adjust the plasma in a substrateprocessing system by using a plasma data monitoring assembly, such as anoptical instrument adapted to measure properties of light over a portionof the electromagnetic spectrum. For example, in one embodiment, amethod may be realized by utilizing wavelength intensities sensitive toRF power that are generated within a chamber. Then, an electronicdevice, for example, a computer software, may analyze the wavelengthintensities and a match circuit may then be adjusted. In this way,consistent (i.e., repeatable) plasma condition may be obtained. In otherembodiments, the present invention may utilize the relationship betweenchamber pressure, substrate temperature, coil currents, electron-neutronratio, electron density, electron energy and/or the plasma in order toadjust and maintain a consistent plasma process.

While the following description of the system is described withreference to a plasma processing chamber (e.g., a Plasma NitridationChamber), the same techniques may be applied to other applications andsystems, such as substrate etch chambers and others, wherein plasma isgenerated.

Although, the present invention is described with reference to a plasmanitridation chamber (e.g., Decoupled Plasma Nitridation (DPN) chamber),it is to be noted that the plasma of the plasma nitridation process maybe generated by various ionizing power sources, which may, for example,include an inductively coupled power source, a capacitatively coupledpower source, a surface wave power source, an electronic cyclotronresonance source (ECR source), magnetron or modified magnetron-typesources, or other sources that may be used to facilitate plasmageneration in a processing chamber.

FIG. 1 illustrates a schematic, cross-sectional diagram of oneillustrative embodiment of a substrate processing system 100 forfabricating integrated devices suitable for use with the presentinvention. The substrate processing system 100 generally includes aplasma processing module, such as a reactor module 101. One illustrativeembodiment of a reactor module 101 that can be used to perform the stepsof the present invention is a Decoupled Plasma Nitridation (DPN) processreactor, made by Applied Materials located in Santa Clara, Calif.

In one embodiment, the reactor module 101 includes a process chamber110, a Radio Frequency (RF) power source 118 (e.g., plasma powersource), and a controller 140. The process chamber 110 may also includea substrate support pedestal 116 within a body (wall) 130, which may bemade of a conductive material. The chamber 110 is supplied with adielectric ceiling 120. In the depicted embodiment, the ceiling 120 issubstantially flat. Other embodiments of the process chamber 110 mayhave other types of ceilings, e.g., a curved or domed ceiling. A lid(not shown) may be additionally provided to house and protect additionalcomponents of the reactor 101 as well as form a shield for RF radiation.Above the ceiling 120 is disposed an antenna comprising at least oneinductive coil element 112 (two co-axial elements 112 are shown). Theinductive coil element 112 is coupled, through a first matching network(e.g., match circuit(s)) 119, to an RF power source 118. In otherembodiments, the reactor module 101 may include a plurality of matchcircuits each having one or more outputs connecting to the coil element112. In another embodiment, the match network 119 may have a singleoutput connecting to the coil element 112. In any case, the plasmasource 118 typically is capable of producing up to 3000 W at 13.56 MHz.

A controller 140 is coupled to the various components of the substrateprocessing system 100 to facilitate control of, for example, theprocessing, monitoring plasma, adjusting the power and frequency of thepower supply and other automated functions as described herein. Thecontroller 140 may include a central processing unit (CPU) 144, a memory142, and support circuits 146 for the CPU 144. The controller mayfacilitate control of the components of the chamber 110 and thenitridation process. The controller 140 may be one of any form ofgeneral-purpose computer processor that can be used in an industrialsetting for controlling various chambers and sub-processors. The memory142, or computer-readable medium of the CPU 144 may be one or more ofreadily available memory such as random access memory (RAM), read onlymemory (ROM), floppy disk, hard disk, or any other form of digitalstorage, local or remote. The support circuits 146 are coupled to theCPU 144 for supporting the processor in a conventional manner. Thesecircuits include cache, power supplies, clock circuits, input/outputcircuitry and subsystems, and the like. The inventive method may bestored in the memory 142 as a software routine (e.g., low power RFtuning software). The software routine may also be stored and/orexecuted by a second CPU (not shown) that is remotely located from thehardware being controlled by the CPU 144. Alternatively, in anotherembodiment, the inventive method may be stored in computer 195 and/orcontroller 140.

In a basic operation (e.g., a substrate implant operation), a substrate114 is placed on the pedestal 116 and process gases are supplied from agas panel 138 through entry ports 126 to form a gaseous mixture 150. Thegaseous mixture 150 is ignited into a plasma 155 in the chamber 110 byapplying power from the plasma source 118 to the inductive coil element112. The pressure within the interior of the chamber 110 is controlledusing a throttle valve 127 and a vacuum pump 136. Typically, the chamberwall 130 is coupled to an electrical ground 134. The temperature of thewall 130 is controlled using liquid-containing conduits (not shown) thatrun through the wall 130.

The temperature of the substrate 114 may be controlled by stabilizing atemperature of the support pedestal 116. In one embodiment, helium gasfrom a gas source 148 is provided via a gas conduit 149 to channels (notshown) formed in the pedestal surface under the substrate 114. Thehelium gas is used to facilitate heat transfer between the pedestal 116and the substrate 114. During processing, the pedestal 116 may be heatedby a resistive heater (not shown) within the pedestal to a steady statetemperature and then the helium gas facilitates uniform heating of thesubstrate 114. Using such thermal control, the substrate 114 may bemaintained at a temperature between about 20 to 350 degrees Celsius.

The RF power source may operate at any suitable frequency, for example,13.56 MHz. In one embodiment, the power is operated at radio frequencyand the power modulation frequency may be typically turned on and off atKHz frequencies. For example, in one embodiment, the RF power source 118may continuously operate at 13.56 MHz while the RF power source 118 maybe pulsed at a frequency of about 1 KHz to about 50 KHz. In otherembodiments, the RF power source 118 may continuously operate withoutpulsing. The peak RF power is typically set between about 50 watts toabout 3000 watts. In some embodiments, effective power (duty cyclemultiplied by the source power) may range from about 10 watts to about30 watts. The duty cycle of the modulations (or pulses) may be betweenabout 2% to about 90% and the ionizing power may be varied between about0% and about 100% to generate the desired mean temperature of theconstituents of the plasma. It is contemplated that a Direct Currentpower source (DC power source) may be utilized in some embodiments ofthe present invention.

In one embodiment, a nitrogen-containing gas, such as N₂ or NH₃ at aflow rate of about 50 sccm to about 20 slm may be introduced to thechamber for processing a substrate located within the chamber. Inaddition to the nitrogen-containing gas, an inert gas, such as He, Ar,Ne (neon), Kr (krypton) or Xe (xenon), may be used to sustain the plasmaand to modify the electron temperature within the chamber. In oneembodiment, the inert gas flow rate is between about 0 sccm and about 20slm. The plasma nitridation process is typically operated at pressurebetween about 1 mTorr to about 1 Torr.

In order to monitor and adjust the plasma generated by a low power RFdevice (e.g., RF power source 118), the present invention may utilize adevice, which is capable of detecting the electromagnetic radiationgenerated by a plasma within the chamber. Electromagnetic radiation maybe a visible light, infrared light, UV light and the like.

In one embodiment, a monitoring system 182 is capable of detecting theradiated electromagnetic radiation by utilizing interferometry. Inanother embodiment, the monitoring system 182 is adapted to monitor theplasma by utilizing spectroscopy (e.g., optical spectroscopy). In oneembodiment, the monitoring system 182 detects a single wavelength ofelectromagnetic radiation from the plasma. In other embodiments, themonitoring system 182 may detect a plurality of wavelengths ofelectromagnetic radiation with various intensities from the plasma. Insome aspects, detecting a plurality of wavelengths of electromagneticradiation may be used advantageously, since the detected electromagneticradiation waves may behave differently for different wavelengths whenmonitoring the plasma. In one embodiment, electromagnetic radiationwaves having wavelengths of between about 200 nm and about 800 nm and insome cases, between 800 nm and 1700 nm, may be used depending on thesources used to generate a plasma within the chamber. In otherembodiments, an average of a plurality of wavelengths may be used tomonitor the plasma and yet in other embodiments, one or more wavelengthsin addition to one or more non-RF related parameters may be utilized tomonitor and/or control the plasma. The monitoring system 182 is capableof using non-reflective RF parameters, spectral and non-spectralparameters in order to monitor and control the plasma.

Depending on the species of gases (e.g., nitrogen) used to generateplasma, a particular wavelength may be selected to monitor the plasma.For example, for a 1^(st) neg N₂ ⁺, an optical filter may be used inorder to detect and monitor wavelengths of about 337.13 nm or of about391.44 nm. Alternatively, for a 1^(st) pos N₂, a wavelength of about590.60 nm or of about 601.36 nm is monitored. Examples of typical gasesthat may be used for plasma processing may include N₂, H₂, He, O₂, CO₂,CH₄ and the like. Thus, the selected wavelengths may vary.

In one embodiment, the monitoring system 182 may include a spectrometer156, a sensor 190 and a computer 195. In one embodiment, the computer195 and controller 140 may be one and the same. However, in oneembodiment, the controller 140 is used for controlling the chamberactivities, while, the computer 195 is used for controlling the plasmamonitoring, data collection and analysis. The computer 195 may include alow power RF tuning module (e.g., low power RF tuning software 180). Thelow power RF tuning software 180 may include an executable programmodule, for example a Dynamic Link Library (DLL) that performs one ormore low power RF tuning functions at runtime. The low power RF tuningsoftware 180 may also be stored and/or executed by a second CPU (notshown) that is remotely located from the hardware being controlled bythe computer 195. In another embodiment, the low power RF tuningsoftware 180 may be stored in controller 140 and/or computer 195. Inother embodiments, the low power RF tuning software 180 may be locatedin spectrometer 156 or RF power source 118 or in the match network 119.Alternatively, the low power RF tuning software may be included in oneor more computers placed within any of the substrate processing'ssubsystems such as RF power source 118 and the like.

FIG. 2 illustrates one embodiment of the present invention with anexemplary schematic diagram of a processing system (processing system200) with an optical port sensor for plasma monitoring. As shown, amonitoring system 280 may utilize a spectrometer 256 to collect theradiation from the generated plasma within the chamber. A fiber opticalsplitter 292 may split the radiation into discrete wavelengths, anddetect the intensity of the radiation at each discrete wavelength. Inone embodiment, the spectrometer 256 may include an input slit, adiffraction grating (or optical prism), a diffraction grating controllerand a detector array to collect the incoming radiation. In oneembodiment the spectrometer 256 is used to scan across a range ofwavelengths of the emitted radiation as a function of time to monitorand control the process. A sensor 290 is adapted to detect a pluralityof wavelengths. Suitable sensors used to measure the various wavelengthsmay include the following classes of sensors, for example, aphotovoltaic, a photoconductive, a photoconductive-junction, aphotoemissive diode, a photomultiplier tube, a thermopile, a bolometer,a pyroelectric sensor or other like detectors. When using sensordetectors of this type, it may be advantageous to use filters to limitdesired wavelengths that are detected. In one embodiment as shown inFIG. 3, sensor 290 may be placed next to a window such that it is indirect view of plasma region through a chamber wall 299. Alternatively,a sensor may be inserted or it may be fully enclosed within theprocessing chamber (not shown). In either case, a fiber optic cable maybe used to transfer the detected signals to a controller, forprocessing, in order to obtain desired processing data used to controlthe plasma.

In one embodiment, the optical interface between the sensor device 290and the spectrometer 256 may be provided using a fiber-optic array 264.The fiber optic array 264 is generally a bundle of optical fibers(detector fibers) that are connected to the spectrometer 256. In oneembodiment, the fiber optic array 264 has a combined diameter of about0.2 millimeters to about 1 millimeter. The size of the fibers may alsovary to assist in the collection of the reflected light. For example,the detector fibers connected to the spectrometer 256 may have adiameter of about 300 microns. In another embodiment, the fiber opticarray 264 may include a single source fiber or an array of source fiberscoupled to the spectrometer 256 without the need for separate detectorfibers.

In operation, light reflected from the illuminated region (the plasma)248 is detected and guided by the detector 290 to the spectrometer 256.The spectrometer 256 detects a broad spectrum of wavelengths of light,enabling the intensities of the plasma to be observed using a wavelengthhaving a strong reflectance signal and/or using multiple wavelengths. Itis contemplated that, more generally, any analyzer capable of analyzingthe reflected light is used to provide data via a serial cable to thecomputer 295.

Although only one spectrometer is illustrated in FIG. 2, it iscontemplated that in other embodiments, one or more fixed spectrometersand/or one or more variable spectrometers or a combination thereof maybe integrated within the substrate processing system 100 for plasmamonitoring.

In one embodiment, output from the spectrometer 256 is delivered to thecomputer 295 or to the controller 240 for analysis and may be used asdata to monitor and adjust the plasma within the chamber as discussedherein. The computer 295 may be a general purpose computer or a specialpurpose computer and generally is configured with similar components asused by the controller 240 described above. In one embodiment, theoutput from the computer 295 is delivered to the controller 240 so thatnecessary process adjustments may be made. In another embodiment, thecomputer 295 and controller 240 may be the same device, containing allthe required software and hardware components necessary to control theprocess and analyze the spectral information. In either case, thecontroller 240 or the computer 295 or any other computers embeddedwithin the processing system may be adapted to include a low power RFtuning module (e.g., low power RF tuning software) for monitoring aprocess and in particular, for low power RF tuning as discussed below.

FIG. 4 illustrates a schematic of the tuning circuit in communicationwith a spectrometer according to an embodiment of the present invention.As shown, an RF match section 419 includes a variable capacitor C₁connected in series to an input capacitor C and an input inductor L withRF input 422. The RF match section may also include a second variablecapacitor C₂ which is connected across the capacitor C₁ and ground. Thecapacitance of C₁ and/or C₂ may be intentionally and repeatedly changedby motors 442, and 443 of a servo unit 444. In other embodiments, bothcapacitors C₁ and C₂ may include movable capacitance plates such thatthe orientation of which are controlled by motors 442 and 443 of a servounit 444. A controller 440, in communication with a low power RF tuningmodule and computer 495, coupled to the servo unit and the spectrometer456, monitors the generated plasma within the chamber and based on thereflected intensity, controls the operation of motors 442 and 443. Inthis way, the controller controls the values of the variable capacitorsC₁ and C₂. For example, in one embodiment, the controller may adjustthese values to provide for a maximum intensity for a particularwavelength in order to ensure that a consistent plasma is generated. Itis also noted that the match circuit may include other elements (e.g.,other reactance elements), in addition to the elements shown in FIG. 4.

In other embodiments, a plurality of match circuits in communicationwith one or more motors may be utilized to maintain a consistent plasma.In addition, it is contemplated that the match circuit(s) may be locatedin RF power source 418. In other embodiments, the frequency of the RFpower source may be varied instead of varying the capacitance of thematch circuit in order to tune the adjusted in order to control theplasma in the chamber. For example, in one embodiment, the frequency ofthe RF power source 418 may be varied from 13.56 MHz to up to about 13.6MHz or down to about 13.5 Mhz in order to adjust the plasma in thechamber. It is also contemplated that the controller may control thevalues of the variable capacitors C₁ and C₂ of the match circuit inaddition to the frequency of the RF power source to maintain aconsistent plasma.

FIG. 5 illustrates a diagram of a match peak find according to anembodiment of the present invention. As illustrated, a normalizedbroadband wavelength is compared with reflected power (Pref (W)) andaccordingly, a series capacitor is varied. The low power RF tuningsoftware is adapted to select series values that provide for a maximumnormalized broadband wavelength where the P_(ref) is minimized. Then,the selected value is used to compare and adjust the series value. Forexample, when the low power RF tuning software is run, the system willfind the optimum series value for a given capacitor by finding theseries setting which maximizes a user selected parameter.

In some embodiments, depending on the process and/or substrate type usedfor processing in the substrate processing chamber 100, differentwavelengths may be selected. For example, after processing a substrateunder a first processing recipe, a different wavelength may be selectedfor plasma monitoring for a second substrate process recipe. In somecases, a different wavelength may be used for different substrate typesprocessed in the substrate processing system.

Other embodiments of the present invention may provide methods andapparatuses that may be utilized to monitor and adjust the plasma in asubstrate processing system by using a relationship between one or morenon-reflected power methods, such as chamber pressure, substratetemperature, coil currents and/or voltage, electron-neutron mass ratio,phase and others in order to adjust and maintain a consistent plasmaprocess. For example, in one embodiment, the substrate processing system100 may provide for a consistent plasma by selecting a series value thatcorresponds to a maximum inner coil current.

FIG. 6 illustrates a diagram of a match peak find according to anotherembodiment of the present invention. As illustrated, the inner coilcurrent (e.g., Current (2)) is compared with a series capacitor. The lowpower RF tuning software 180 is adapted to select series values thatprovide for a maximum coil current. Then the selected value is used tocompare and/or adjust the series value. For example, when the low powerRF tuning software is run, the system will find the optimum series valuefor a given capacitor (e.g., shunt capacitor) by choosing a seriessetting which maximizes a user selected parameter (e.g., Current (2)).It is contemplated that more than one variable may be monitored in orderto adjust and maintain a consistent plasma. For example, in oneembodiment, optimum match settings may correspond to the series and shutvalues at which, the reflected power is at minimum, the inner coilcurrent and/or the wavelength intensities of a broadband electromagneticreflect are at a maximum.

In other embodiments, the present invention may be used as a monitoringdevice to monitor the plasma. For example, the substrate processingsystem may monitor an expected response (e.g., a predeterminedwavelength intensity). The computer 195 may monitor the reflectedelectromagnetic radiation and once a predetermined deviation from theexpected response is detected, an alert may be sent to a computersystem. In other embodiments, the computer 195 may utilize a dynamicloop and continually adjust the tuning circuits to maintain apredetermined wavelength intensity.

FIG. 7 illustrates operations 700 according to an implementation of thepresent invention. The operations of 700 may be performed, for example,by the controller 140. Moreover, various steps in the methods set forthbelow need not be performed or repeated on the same controller. Theseoperations may be performed before and/or after processing of one ormore substrates. Alternatively, in some cases, after cleaning of thesubstrate processing chamber, one or more of the following steps may beperformed. In addition, the operations 700 may be understood withoccasional reference to FIGS. 1, 4, 5 and 6.

The operations begin, at step 720, where plasma is generated within thesubstrate processing system 100. A substrate 114 may be placed on thepedestal 116 and process gases are supplied from a gas panel 138 throughentry ports 126 to form a gaseous mixture 150. The gaseous mixture 150is ignited into plasma in the chamber 110 by applying power from the RFpower source 118 to the inductive coil element 112.

At step 740, the light reflected from the plasma may be detected and/orcollected by a signal monitoring device via sensor 190 in the form of alight signal(s) and the signal may be transmitted by a signal cable 164to the spectrometer 156. Then, the signal may be analyzed by thespectrometer 156 and the computer 195. At step 760, a low power RFtuning module (e.g., low power RF tuning software 180) may use one ormore of such signals as input data and adjust the matching circuit, forexample, by adjusting C₁ and/or C₂. In some embodiments, the analyzedresults can be used to generate control commands to tune the plasma andadjust the matching circuit. In addition, the control commands maycontrol the reactor chamber via controller 140. In order to monitor andadjust the plasma in a substrate processing system 100, the system mayutilize a plasma data collecting assembly, adapted to measure propertiesof light over a specific portion of the electromagnetic spectrum.

In other embodiments, the present invention may utilize the relationshipbetween chamber pressure, substrate temperature, or antenna current andthe plasma in order to adjust and maintain a consistent plasma process.For example, the plasma monitoring assembly may monitor current throughthe outer antenna and the current through inner antenna (e.g., coilcurrents) in order to monitor and adjust the plasma. A current sensormay be used in the processing system to monitor and report the sensedcurrent to the computer. Then, the low power RF tuning software maymonitor the sensed current in the coils and accordingly adjust theseries value to find an RF match peak. For example, the low power RFtuning software may sequence through a number of series values andmonitor and/or record a decrease in the current. Then, after apredefined number of decreasing steps, locate a peak value. In oneembodiment, the value may be recorded and used as a reference point forfuture tuning runs.

In some embodiments of the present invention, optimum match settings maycorrespond to the series and shut capacitor values where the reflectedpower is minimum, inner coil current is maximum and a broadband signalintensity is maximum. In addition, in other embodiments, the controllermay monitor variables such as coil currents, broadband signalintensities, reflected power, chamber pressure and substrate temperaturealone or in combination in order to provide for an optimum matchsettings. It is noted the present invention may utilize other parametersthat can be mapped to plasma repeatability. In addition, it is alsocontemplated that other measurable characteristics of plasma may be usedto provide for desired match settings.

Embodiments of the present invention provide methods and apparatusesthat may be utilized to monitor and adjust the plasma in a substrateprocessing system. By using a plasma data monitoring assembly,information about the plasma may be monitored and then plasma may beadjusted. In some embodiments, a method may be realized by utilizingwavelength intensities sensitive to RF power that are generated within achamber. Then, an electronic device, for example a computer software mayanalyze the wavelength intensities and a match circuit may then beadjusted. In this way, consistent plasma may be obtained. In otherembodiments, the present invention may utilize the relationship betweenchamber pressure, coil currents, substrate temperature, and the plasmain order to adjust and maintain a consistent (e.g., repeatable) plasmaprocess.

Although the embodiments disclosed above, which incorporate theteachings of the present invention, have been shown and described indetail herein, those skilled in the art can readily devise other variedembodiments which still incorporate the teachings and do not depart fromthe spirit of the invention.

1. A method for monitoring a plasma in a substrate processing system, comprising: monitoring a first plasma condition generated by an inductively coupled plasma within a chamber, the chamber having: one or more walls connected by a dielectric ceiling; and one or more coil elements disposed outside the chamber; associating the first plasma condition to an RF power within the processing system; adjusting a matching circuit to obtain a repeatable plasma condition; monitoring a second plasma condition generated by the inductively coupled plasma within the chamber by monitoring current to the one or more coil elements; and adjusting one or more capacitors coupled to the one or more coil elements to maintain the repeatable plasma condition.
 2. The method of claim 1, wherein the first or second plasma condition has a wavelength between about 200 nm and about 800 nm and the substrate processing system is adapted to detect the wavelength.
 3. The method of claim 1, wherein the monitoring the first or second plasma condition comprises utilizing an interferometer.
 4. The method of claim 1, wherein the monitoring the first or second plasma condition comprises utilizing a spectrometer.
 5. The method of claim 1, wherein the adjusting the matching circuit is performed before and after processing of a substrate.
 6. The method of claim 1, wherein the substrate processing system is a plasma nitridation chamber.
 7. The method of claim 1, wherein the RF power has an effective power of about 5 Watts to about 30 kilo Watts.
 8. The method of claim 1, wherein the monitoring the first or second plasma condition comprises utilizing a current sensor.
 9. An apparatus for monitoring a plasma in a substrate processing system, comprising: a plasma chamber comprising a plurality of walls, at least one wall having a dielectric ceiling; one or more coil elements disposed outside the chamber; a current sensor coupled to each of the one or more coil elements; an RF power source; and one or more adjustable capacitors coupled to each of the one or more coil elements.
 10. The apparatus of claim 9, wherein the each of the adjustable capacitors further comprise: a movable capacitance plate.
 11. The apparatus of claim 10, wherein the movable capacitance plate is coupled to a motor.
 12. The apparatus of claim 9, wherein the chamber further comprises an optical sensor positioned outside of the chamber.
 13. The apparatus of claim 12, wherein the optical sensor comprises a spectrometer.
 14. The apparatus of claim 9, wherein the substrate processing system is a plasma nitridation chamber.
 15. The apparatus of claim 12, wherein the optical sensor is adapted to detect electromagnetic radiation reflected from the inductively coupled plasma with wavelengths between about 200 nm and about 800 nm.
 16. The apparatus of claim 9, wherein the RF power source has an effective power of about 5 Watts to about 30 kilo Watts.
 17. An apparatus for monitoring a plasma in a substrate processing system, comprising: a plasma chamber having a plurality of walls, at least one of the plurality of walls having a dielectric ceiling; at least one inner coil element and at least one outer coil element disposed outside the chamber; a current sensor coupled to one of the inner coil element or the outer coil element, the current sensor adapted to detect current from an inductively coupled plasma generated in the plasma chamber; an RF power source; and one or more adjustable capacitors coupled to each of the one or more coil elements.
 18. The apparatus of claim 17, wherein the each of the adjustable capacitors further comprise: a movable capacitance plate.
 19. The apparatus of claim 18, wherein the movable capacitance plate is coupled to a motor.
 20. The apparatus of claim 17, wherein the chamber further comprises an optical sensor positioned outside of the chamber. 